node.js callback and recursion

Question

I am using the google api to get a list of all the messages in my mailbox. The API is paginating the list, and with every call it returns the next page, so I have to call it recursively:

const fetch = (cb, next) => {
    google.gmail('v1').users.messages.list({
        auth: oauth2Client,
        userId: 'me',
        pageToken: next
    }, cb)
}
const store = (err, result) => {
    // do something with result and then
    if (result.nextPageToken) {
        fetch(store, result.nextPagetToken)
    }
}

fetch(store)

Is there a better way to do this to avoid the recursion so I don't bust the stack?

rsp · Accepted Answer · 2017-03-15 10:26:01Z

1

Instead of:

fetch(store, result.nextPagetToken)

you can use:

process.nextTick(fetch, store, result.nextPagetToken);

but if something like that is already done in messages.list() callback then it may not even be necessary. Besides a proper tail call optimization is already supported in JS and is available in Node since version 6.5.0 when you use the --harmony flag, see:

http://node.green/#ES2015-optimisation-proper-tail-calls--tail-call-optimisation-

And there is also my tco module for infinite recursion even in the oldest versions of Node.

answered Mar 15, 2017 at 10:26

rsp

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1 Comment

599644 Over a year ago

process.nextTick(fetch, store, result.nextPagetToken); looks like exactly what I was looking for. A bit scared to use tail-call-recursion, as I am afraid it will be too easy to break it at some point without noticing. Thanks.

Dom Vinyard · Accepted Answer · 2017-03-15 10:26:49Z

1

I'm afraid I don't know the google API but generally speaking you should be looking at Promises:

Using Promises | Google API

answered Mar 15, 2017 at 10:26

Dom Vinyard

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2 Comments

599644 Over a year ago

Thanks. I was trying to avoid using promises.

Dom Vinyard Over a year ago

Don't avoid it, and don't go ahead with the accepted answer until you've at least tried. Trust me: crack your knuckles and spend one afternoon learning promises. It's a 'pokemon evolution' style change to the language, you will never ever look back.

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